The present invention relates generally to a package of an electronic device, and more particularly, to a package structure and method for a card.
A package of a card-sized electronic device has to provide essential mechanical strength and electric performance, at least conformed to some specific standards and criterion. The structure of the package also has to be used adaptively for package process in order for mass production, and the cost-effectiveness is particularly important. Card-sized electronic devices, such as modem card, LAN care, and memory card, are widely used, and the trend is toward downsizing for such devices. Personal Computer Memory Card International Association (PCMCIA) and compact flash (CF) are typical international standards for memory cards, and new standards are still emerging. While some details exist among various card standards, their package structures are similar, in which a printed circuit board (PCB) is encapsulated with a case whose cover is electrically conductive and provides a ground sidepiece to be electrically connected with the system reference in the slot of the apparatus inserted with the card.
A conventional package method sandwiches a PCB between two plastic frames with two metal covers thereon riveted by a tool so as to encapsulate the plastic frames and PCB. However, the metal covers and plastic frames cannot be tightly bonded by riveting. As a result, the metal covers are likely to loosen and become separated from the package. Moreover, the riveting process may deform the metal covers, and the mechanical strength of the package formed by riveting is poor.
An improvement for the package method applies high temperature adhesive on the internal surface of a metal cover. In a package process, the metal cover is heated to over 80xc2x0 C. to melt the adhesive for attachment of the metal cover with a plastic frame thereon, and then two metal covers with each a plastic frame thereon are riveted to encapsulate a PCB therebetween after a cooling process to confirm the adhesives between the metal covers and plastic frames. The prior art requires heating and cooling processes, which is somewhat bothersome and time-consuming. In addition, possibilities are inherent that the attached plastic frame on the metal cover may be dropped from the cover during the riveting process, thus poor performance is still employed.
Further improved package structure and method are proposed respectively in U.S. Pat. Nos. 5,397,857, 5,475,919, and 5,490,891, by which a metal cover is positioned in a mold to be directly bonded with a plastic frame with an injection molding such that a half case is formed, and then a package is completed with two half cases by combining the plastic frames respectively on the two half cases together by sonic welding. Such package offers better mechanical strength and simpler manufacture process than prior arts, while in payment of higher technique and more cost for material and manufacture. At first, the metal cover has to be formed with hooks or curved fingers on each sides to be embedded into the plastic frame during direct injection molding, so as to be firmly bonded itself with the plastic frame. For the formation of such hooks or fingers on each side of a metal cover, a longer metal plate enough for the length of the hooks or fingers is used and bent many times. Therefore, the manufacture process of the metal cover is more time-consuming, complex, and difficult, cost for material and manufacture is also more, tools to be used in the process are larger, and there is more attrition to the tools. In addition, the precision requirement for the metal cover to be positioned in the mold with the plastic frame injection molded thereon is critical and strict. Further, in order for electrical connection between two metal covers by contact with each other and welded combination of two plastic frames respectively on the covers at the same time, the precision requirement for the metal cover is more critical and strict. Also, molds with high precision for such metal covers and plastic frames are very expensive, which thus increases the manufacture cost. Finally, each time only one metal cover can be enclosed within the cavity of a mold for injection molding with such prior arts. In this manner, a mold can injection-mold only one plastic frame each time, which is adverse to mass production. Therefore, it is desired alternative approach or improvement on package structure and method for a card.
One object of the present invention is to provide a package structure and method for a card advantageous to manufacture process, time, cost, and reliability. According to the present invention, a package structure and method for a card comprises respective attachment of first and second conductive covers each having a vertical piece extending on one side thereof with first lateral surface of first and second plastic frames in use of a low temperature adhesive therebetween to form first and second half cases, and combination of the first and second half cases with insertion of another adhesive or sonic welding between second lateral surfaces of the first and second plastic frames. Preferably, one welding line is formed or one chemical is applied on one or both of the second lateral surfaces of the first and second plastic frames in order for sonic welding of the first and second plastic frames. Alternatively, one adhesive area is formed along and deep into one or both of the second lateral surfaces of the first and second plastic frames in order for adhesion of the first and second plastic frames with the another adhesive.
Further to the first and second lateral surfaces, the plastic frame has an outer surface preferably formed with a recess to accommodate the vertical piece of the conductive cover, by which the outer surface of the vertical piece is not lower than the outer surface of the plastic frame. An adhesive area is formed preferably deep into the plastic frame to be coated with the low temperature adhesive in order for the attachment of the conductive cover.
Each of the first and second plastic frames is further formed with a trench or through hole for clamping a conductive piece, preferably with a hook shape, in contact with the conductive cover and the other conductive piece on the other plastic frame.
Preferably, the second lateral surfaces of the first and second plastic frames have corresponding positioning holes and heads so as to bond the plastic frames together.